Using freshwater to process shit is a waste of water humanity can no longer afford

"Less than 3 per cent of Earth's water is fresh, and only a tiny portion of that is easily available to us. Most of the water that standard sewage systems use to move human waste is drinkable. Diminishing water resources mean alternatives are pressingly needed. Wastewater gardens, where marsh plants are used to filter lavatory output and allow cleaned water to enter natural watercourses, are very much part of that solution."

Beautiful and edible plants can grow out of excrement (Image: Gonzalo Areil

Book information
The Wastewater Gardener: Preserving the planet, one flush at a time
by Mark Nelson
Published by: Synergetic Press

Price: $23.95

Book Review

A globetrotting, water-saving tour of sewage gardens

by Adrian Bennett

August 4, 2014

New Scientist

Would you dine in an artificial wetland laced with human waste? In The Wastewater Gardener, Mark Nelson makes an inspiring case for a new ecology of water

RAINFOREST destruction, melting glaciers, acid oceans, the fate of polar bears, whales and pandas. You can understand why we get worked up about them ecologically. But wastewater?

The problem is excrement. Psychologically, we seem to be deeply averse to the stuff and want to avoid contact whenever possible – we don't even want to think about it, we just want it out of the way.

The solution, a universal pipe-based waste network, works well until domestic and industrial chemicals and other non-biological waste are mixed in. Treating the resulting toxic soup, as Mark Nelson explains in The Wastewater Gardener, is not only a major technological challenge, but also uses enormous amounts of one of the planet's most limited resources: fresh water.

Each adult produces between 200 and 500 grams of faeces per day. With our current population, that's a yearly 500 million tonnes. Centralised sewage systems use between 1000 and 2000 tonnes of water to move each tonne of faeces, and another 6000 to 8000 tonnes to process it.

Even then, this processed waste often ends up in waterways, affecting wildlife and communities downstream, and it eventually finds its way to the ocean. There it contributes to the process of eutrophication, which creates dead zones, killing coral reefs and other sea creatures.

But it doesn't have to be like that. As head of Wastewater Gardens International, Nelson has travelled the world, developing and promoting artificial wetlands as the most logical way to use what we otherwise flush away.

Except that, as Nelson points out, with 7 billion-plus people, there really is no "away". Besides, what the public purse pays to detox and dump can be put to profitable work, fertilising greenery for urban spaces and fruits and vegetables for domestic and commercial use, for example.

Less than 3 per cent of Earth's water is fresh, and only a tiny portion of that is easily available to us. Most of the water that standard sewage systems use to move human waste is drinkable. Diminishing water resources mean alternatives are pressingly needed. Wastewater gardens, where marsh plants are used to filter lavatory output and allow cleaned water to enter natural watercourses, are very much part of that solution.

Nelson clearly understands the yuck factor and goes to great lengths to show that having a shallow vat of human-waste-laced water nearby is far less vile than we might imagine, especially when it is covered by gravel and interlaced with plant roots. Restaurants with tables dotted between ponds containing the ever-filtering artificial wetlands provide convincing proof.

Constructed wetlands can take on big jobs, too: a mixture of papyrus, lotus and other plants have successfully and beautifully detoxified water from Indonesian batik-dying factories. This water had killed cows downstream and caused running battles between farmers and factory workers.

The Wastewater Gardener is not a "how to" story, but more a "how it was done" account. Nelson tells how these wetlands started to become mainstream in less than 30 years. With humility and humour, he recounts how, as a boy from New York City, he acquired hands-on ranching knowledge in New Mexico, then studied under American ecology guru, Howard Thomas Odum.

And stories of his experiences everywhere from urban Bali and the Australian outback to Morocco's Atlas mountains and Mexico's Cancún coast illustrate the gravelly, muddy evolution of his big idea. An inspiring read, not just for the smallest room.

This article appeared in print under the headline "Excellent excrement"

Adrian Barnett is a rainforest ecologist at Brazil's National Institute of Amazonian Research in Manaus

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